Building an extension using 300mm thermalite blocks
- Thread starter DIYedboy
- Start date
Because you don't need 300mm block for a compliant solid wall. You only need a 215mm thick block with around 60mm of internal insulation.
Forgive my ignorance, but, I thought if you use 215mm blocks you need 100mm of kingspan on the inside or if you use 300mm blocks you only need 50mm kingspan, am I wrong?
On a seperate note, will a 100mm thermalite block that is unfinished allow rain penetration through to the inside face?
On a seperate note, will a 100mm thermalite block that is unfinished allow rain penetration through to the inside face?
You are wrong. 100mm of AAC block is nothing like as efficient an insulator as 50mm of Kingspan. 100mm of AAC block is actually about as effiecient as 10-15mm of Kingspan.
They say that AAC blocks do not allow water to penetrate, but that isn't the only issue. You've still got the mortar joints through which water could penetrate.
100mm blockwork or brickwork can be used as a cladding, but there will be further structure as an inner leaf whether it's timber frame or lightweight steelwork between an RC or structural steel frame.
Whatever the construction, there should be a detail that ensures any water getting through to the inside face will be guided back to the outside.
RR, we have a misunderstanding, I looked on some block manufacturers sites and I thought they were saying 'if you use our 215mm block you need 100mm of kingspan attached to the inside face of that wall to comply with U value requirements, if a 300mm block is used only 50mm of kingspan needs to be attached (directly to wall surface)'.
Good point, the block may not transmit, but the mortar could do!
Good point, the block may not transmit, but the mortar could do!
There would have to be a large difference in the thermal conductivity of the 215mm and the 300mm blocks for this to be the case. If the thermal conductivity was the same, as I said above, 10-15mm of additional Kingspan would be all that you would require to give you the same U-value if using 215mm blocks compared to 300mm. And you end up with a thinner wall.
Have you got a link to that site? I'd like to see for myself what it says.
I've just looked on the celcon and thermalite sites and both say 215mm blocks and 50mm thermal boards and as you say RR the difference using 300mm blocks is negligible, thank god I asked the question, now I stand corrected!
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